A dielectric ceramic composition consisting essentially of: PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3 wherein x+y+z=1, which allows low-temperature sintering and has a high dielectric constant, a low dielectric loss and a high specific resistivity.

Description

9 parts

›FIELD OF THE INVENTION AND RELATED ART STATEMENT

1. Field of the Invention

The present invention relates to dielectric ceramic compositions capable of sintering at low-temperature, exhibiting a high dielectric constant, low temperature coefficient of the dielectric constant and low dielectric loss, and being suitable for use in ceramic capacitors. 2. Description of the Related Art

As promising ceramic compositions for the above-mentioned purpose, those essentially consisting of BaTiO 3 have been widely used as substance of high dielectric constant. The dielectric constant of this substance has a relatively high temperature coefficient of the dielectric constant, while in general, a dielectric substance which exhibits a low temperature coefficient of the dielectric constant has a relatively low dielectric constant.

The temperature coefficient of a ceramic capacitor is established or defined by JIS (Japanese Industrial Standard) or EIA (U.S. Electronics Industries Association) Standard. For example, the temperature coefficient of a dielectric constant adaptable to YF rating of JIS, which is approximately equivalent to Y5 V rating of EIA Standard, means that the temperature coefficient varies within a range of +22 to -82% for operating range of -30° C. to 85° C. A dielectric material which exhibits a dielectric constant of 10,000, is adaptable to YF or Y5 V. However, BaTiO 3 system ceramics must be sintered at a very high temperature in the range of 1300° C. to 1400° C., so that where they are used as a dielectric substance of multilayer ceramic capacitors, expensive metals such as platinum or palladium which can stand such high sintering temperature must be used as internal electrodes of the capacitors, thereby obstructing cost reduction. Therefor there has still been a demand for dielectric ceramic materials which can be sintered at a temperature as low as below 1100° C. for enabling the use of relatively cheap metal such as silver-30% palladium for the internal electrodes.

U.S. Pat. No. 4,078,938 discloses binary system ceramic compositions of Pb(Fe 2/3 Nb 1/3 )O 3 -Pb(Fe 1/2 W 1/2 )O 3 which can be sintered at a temperature as low as below 1000° C., and which exhibit a high dielectric constant of 20,000. However, the resultant ceramics have a relatively low specific resistivity.

U.S. Pat. No. 4,265,668 discloses binary system ceramic composition PbTiO 3 -Pb(Mg 1/3 Nb 2/3 )O 3 , which exhibit a high dielectric constant of 20,000.

However, the ceramic compositions of this binary system must be sintered at a temperature range of 1100° C. to 1150° C.

U.S. Pat. No. 4,450,240 discloses ternary system ceramic compositions of PbTiO 3 -Pb(Ni 1/3 Nb 2/3 )O 3 -Pb(Mg 1/2 W 1/2 )O 3 , which can be sintered at a temperature range of 900° C. to 1050° C. and exhibit a high electrical resistivity. However, the ceramics have a dielectric constant under 15,000.

›SUMMARY AND OBJECT OF THE INVENTION

The object of the present invention is to provide a dielectric ceramic composition which can be sintered at a temperature as low as below 1100° C., and exhibits high dielectric constant and a high specific resistivity.

To attain the object, a ceramic composition of the present invention is a dielectric ceramic composition essentially comprising a substance represented by the formula.

PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1.00.

Other mode of the present invention contains MnO 2 , Cr 2 O 3 , CoO And MoO 3 as an additive.

Still other mode of the invention contains Pb(Mn 1/3 Nb 2/3 )O 3 .Pb(Mn 1/2 Sb 2/3 )O 3 as an additive.

These novel composition of the present invention can be sintered at a temperature in the range from 900° C. to 1100° C., and have a high dielectric constant up to 8,000, and low temperature coefficient of the dielectric constant which meet the YF rating of JIS or Y5 V rating of EIA standard, and further it has a high specific resistivity.

›BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawing is a composition diagram of PbTiO 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -Pb(Ni 1/2 W 1/2 )O 3 ternary system, wherein the polygon ABCDE shows a range of composition of the ceramic composition in accordance with the present invention.

›DETAILED DESCRIPTION OF THE INVENTION

The composition herein may be prepared in accordance with various well-known ceramic procedures.

›Examples5

›EXAMPLE 1

The starting materials, viz. lead oxide (PbO), titanium oxide (TiO 2 ), niobium oxide(Nb 2 O 5 ), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO 3 ), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range of 750° C. to 880° C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm 2 . After buring out the binder at about 700° C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900° C. to 1100° C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 1. The dielectric constant (ε) and the dielectric loss (tan δ) were measured at a frequency of 1 KHz and a voltage of 1 V at 20° C. The temperature coefficients of the dielectric constant were obtained by measuring the dielectric constants at temperatures in the range of -25° C. to 85° C. and then calculations are made with reference to the dielectric constant at 20° C.

The sintering temperature is selected as the temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20° C. under application of a D.C. voltage of 1000 V.

From TABLE 1 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing provide a

__________________________________________________________________________

Sintering tan δ

Change of Specific

Composition temperature

20° C.

ε (%)

resistivity

No.

x y z (°C.)

20° C.

(× 10.sup.-4)

(-25° C.)

(+85° C.)

(Ω · cm)

__________________________________________________________________________

1 0.025

0.950

0.025

1090 10780

400 -5.4 -34.0 6.0 × 10.sup.12

0.070

0.930

0.000

1150 21040

460 -54.6 -57.4 4.5 × 10.sup.11

3 0.125

0.850

0.025

1090 17730

500 -66.0 -28.1 2.0 × 10.sup.13

0.350

0.600

0.050

1100 3200

640 -12.5 +128.2

8.0 × 10.sup.12

5 0.375

0.450

0.175

980 10210

500 -74.3 -11.6 5.0 × 10.sup.12

6 0.200

0.700

0.100

1000 21350

410 -60.0 -54.0 1.0 × 10.sup.13

7 0.250

0.550

0.200

980 12110

90 -12.0 -55.0 8.0 × 10.sup.12

8 0.200

0.550

0.250

900 9850

45 -8.1 -60.3 2.5 × 10.sup.12

0.100

0.600

0.300

900 4930

40 +121.2

-45.0 1.4 × 10.sup.12

10 0.025

0.900

0.075

1030 11450

50 -13.3 -61.2 1.5 × 10.sup.13

11*

0.000

0.930

0.070

1030 9660

50 -4.3 -89.6 1.2 × 10.sup.13

12*

0.400

0.300

900 8760

102 -12.6 -45.3 1.0 × 10.sup.12

__________________________________________________________________________

Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y

(Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

Note 2: Compositions of the Nos. with an asterisk (*) are outside the

scope of the present invention. high dielectric constant (ε=

9850-21350), high specific resistivity, low dielectric loss (tan

δ≦500×10), low temperature coefficient of the

dielectric constant which is adaptable to YF ranges rating of JIS and Y5 V

rating of EIA Standard, and can be sintered below 1100° C., for

which the points A, B, C, D and E of FIG. 1 are represented by the values

of x, y and z as shown in TABLE 2.

The reasons for the limitations of values in TABLE 2 are as follows.

In case of the composition wherein proportions of z is smaller than 0.025 such as sample No. 2, the sintering temperature is higher than 1100a° C. Such compositions, which lie outside of line BC, DE and EA of the polygon ABCDE in the ternary system composition diagram as samples No. 4, 9 and 11, exhibit high temperature coefficients of dielectric constant. Such composition, which lies outside of line CD of the polygon ABCDE in the ternary system composition diagram, as sample No. 12 exhibits a dielectric constant which is lower than 9500.

›EXAMPLE 2 · 1 of 2

______________________________________

x y z

______________________________________

A 0.025 0.950 0.025

B 0.125 0.850 0.025

C 0.375 0.450 0.175

D 0.200 0.550 0.250

E 0.025 0.900 0.075

______________________________________

oxide(CoO) and molybdenum oxide(MoO 3 ), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range 750° C. to 880° C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm 2 . After buring out the binder at about 700° C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900° C. to 1100° C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 3. The dielectric constant and the dielectric loss were measured at a frequency of 1 KHz and a voltage of 1 V at 20° C. The temperature coefficients of the dielectric constants were obtained by measuring a dielectric constant at temperatures in the range of -25° C. to 85° C. and calculated with reference to the dielectric constant at 20° C.

The sintering temperature is selected as the

__________________________________________________________________________

Sintering Specific

Additive

tempera- tan δ

Change of resistivity

Composition element

ture ε

20° C.

ε (%)

tivity

No.

x y z wt % (°C.)

20° C.

(× 10.sup.-4)

(-25° C.)

(+85° C.)

(Ω · cm)

__________________________________________________________________________

0.100

0.800

0.100

-- -- 1050 13930

310 +8.4 -54.1 1.2 × 10.sup.13

2 0.100

0.800

0.100

MnO.sub.2

0.05

1050 12230

122 +7.3 -48.3 1.2 × 10.sup.13

3 0.100

0.800

0.100

MnO.sub.2

0.20

1040 12100

63 +4.1 -43.0 1.4 × 10.sup.13

0.100

0.800

0.100

MnO.sub.2

1.00

1010 5440

210 +5.1 -21.3 2.0 × 10.sup.12

0.100

0.800

0.100

Cr.sub.2 O.sub.3

0.01

1040 13320

250 +8.1 -54.0 1.1 × 10.sup. 13

6 0.100

0.800

0.100

Cr.sub.2 O.sub.3

0.03

1030 13030

170 +5.1 -45.3 1.0 × 10.sup.13

7 0.100

0.800

0.100

Cr.sub.2 O.sub.3

0.15

1030 12420

102 +4.1 -45.4 7.5 × 10.sup.12

0.100

0.800

0.100

Cr.sub.2 O.sub.3

0.70

1000 11450

340 +7.1 -21.9 2.5 × 10.sup.11

0.100

0.800

0.100

CoO 0.02

1050 12980

280 +7.5 -49.3 1.0 × 10.sup.13

10 0.100

0.800

0.100

CoO 0.40

1010 11390

175 +4.3 -40.6 1.0 × 10.sup.13

11*

0.100

0.800

0.100

CoO 0.90

1000 5480

100 +12.5 -21.8 3.5 × 10.sup.11

12*

0.100

0.800

0.100

MoO.sub.3

0.01

1050 13640

300 +8.0 -54.1 1.1 × 10.sup.13

13 0.100

0.800

0.100

MoO.sub.3

0.40

1000 10960

180 +12.5 -43.7 8.5 × 10.sup.12

14*

0.100

0.800

0.100

MoO.sub.3

0.90

960 6490

250 +13.2 -31.7 8.0 × 10.sup.11

15 0.100

0.800

0.100

MnO.sub.2

0.10

CoO 0.05

1030 13340

100 +6.3 - 51.0

1.0 × 10.sup.13

16#

0.200

0.700

0.100

-- -- 1000 21350

410 -6.3 -54.0 1.0 × 10.sup.13

17*

0.200

0.700

0.100

MnO.sub.2

0.01

1000 21000

400 -6.2 -53.3 1.1 × 10.sup.13

18 0.200

0.700

0.100

MnO.sub.2

0.03

1000 20000

200 -6.0 -51.4 1.5 × 10.sup.13

19 0.200

0.700

0.100

MnO.sub.2

0.10

1000 19050

145 -0.4 -49.3 1.2 × 10.sup.13

20 0.200

0.700

0.100

MnO.sub.2

0.60

1000 8430

73 +1.5 -39.3 5.0 × 10.sup.12

21*

0.200

0.700

0.100

MnO.sub.2

1.00

980 5430

150 +7.8 -21.3 8.0 × 10.sup.11

22*

0.200

0.700

0.100

Cr.sub.2 O.sub.3

0.02

1000 20640

315 -5.3 -51.3 1.4 × 10.sup.13

23 0.200

0.700

0.100

Cr.sub.2 O.sub.3

0.30

950 14350

183 +9.3 -41.7 1.4 × 10.sup.13

24*

0.200

0.700

0.100

Cr.sub.2 O.sub.3

0.70

900 11430

235 +15.3 -30.8 7.0 × 10.sup.11

25*

0.200

0.700

0.100

CoO 0.01

1000 21430

315 -8.3 - 53.2

1.1 × 10.sup.13

26 0.200

0.700

0.100

CoO 0.25

980 20180

175 -5.4 -51.3 1.0 × 10.sup.13

27*

0.200

0.700

0.100

CoO 0.80

960 18930

220 -4.3 -50.6 3.0 × 10.sup.11

28*

0.200

0.700

0.100

MoO.sub.3

0.01

980 20740

325 -6.0 -53.1 8.5 × 10.sup.13

29 0.200

0.700

0.100

MoO.sub.3

0.40

950 16340

163 +3.1 -50.4 1.1 × 10.sup.12

30*

0.200

0.700

0.100

MoO.sub.3

1.00

910 13320

230 +5.1 -48.3 4.0 × 10.sup.11

31#

0.250

0.550

0.200

-- -- 980 12110

90 +4.4 -55.0 8.0 × 10.sup.12

32 0.250

0.550

0.200

MnO.sub.2

0.08

970 10940

32 +3.2 -48.3 8.5 × 10.sup.12

33 0.250

0.550

0.200

MnO.sub.2

0.40

950 8460

21 +0.3 -40.3 8.0 × 10.sup.11

34*

0.250

0.550

0.200

MnO.sub.2

0.80

940 5540

83 -0.9 -31.3 1.0 × 10.sup.11

35*

0.250

0.550

0.200

Cr.sub.2 O.sub.3

0.01

980 12330

87 +4.4 -55.3 8.0 × 10.sup.12

36 0.250

0.550

0.200

Cr.sub.2 O.sub.3

0.03

980 12120

74 +4.0 -51.3 1.0 × 10.sup.13

37 0.250

0.550

0.200

Cr.sub.2 O.sub.3

0.15

970 10770

40 +3.1 -43.3 1.3 × 10.sup.13

38 0.250

0.550

0.200

Cr.sub.2 O.sub.3

0.50

950 8960

85 +1.0 -38.8 4.5 × 10.sup.12

39*

0.250

0.550

0.200

Cr.sub.2 O.sub.3

1.00

930 5140

250 -3.5 -31.5 2.0 × 10.sup.11

40 0.250

0.550

0.200

CoO 0.30

960 11540

174 -3.1 -42.3 8.0 × 10.sup.12

41 0.250

0.550

0.200

CoO 0.50

960 10430

184 -6.3 -38.4 9.0 × 10.sup.11

42*

0.250

0.550

0.200

CoO 0.80

970 9440

230 -7.4 -36.5 1.5 × 10.sup.10

43*

0.250

0.550

0.200

MoO.sub.3

0.02

980 11340

210 +3.1 -53.2 8.5 × 10.sup.12

44 0.250

0.550

0.200

MoO.sub.3

0.15

960 10420

152 +7.3 -48.1 1.2 × 10.sup.12

45*

0.250

0.550

0.200

MoO.sub.3

0.80

960 5110

135 +4.3 -31.2 7.0 × 10.sup.11

__________________________________________________________________________

Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y

(Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

Note 2: Compositions of the Nos. with asterisk (*) are outside the scope

of the present invention, with sharp (#) are included in the claim 1.

temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20° C. under application of a D.C. voltage of 1000 V.

From TABLE 3 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing and containing at least one element selected from the group consisting of Mn, Cr, Co and Mo in an amount in total equivalent 0.03 to 0.06 weight % of respective oxides (MnO 2 , Cr 2 O 3 , CoO and MoO 3 ) exhibit low dielectric loss at the room temperature as compared with that of composition with no addition and exhibit still high dielectric constant even with low sintering temperature.

›EXAMPLE 2 · 2 of 2

The reasons for the limitations in TABLE 3 are as follows.

If content of MoO 2 , Cr 2 O 3 , CoO and MoO 3 in total is smaller than 0.03 weight %, the dielectric loss at the room temperature is not improved. When the content in total is larger than 0.60 weight %, the dielectric loss becomes larger and specific resistivity becomes smaller.

›EXAMPLE 3 · 1 of 2

The starting materials, viz. lead oxide(PbO), titanium oxide(TiO 2 ), niobium oxide(Nb 2 O 5 ), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO 3 ), manganese oxide(MnO 2 ) and antimony oxide(Sb 2 O 5 ), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range 750° C. to 880a° C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm 2 . After buring out the binder at about 700° C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900° C. ato 1100° C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 4. The dielectric constant and the dielectric loss were measured at a frequency of 1 KHz and a voltage of 1 V at 20° C. The temperature coefficients of the dielectric constants were obtained by measuring a dielectric constant at temperatures in the range of -25° C. to 85° C. and calculated with reference to the dielectric constant at 20° C.

__________________________________________________________________________

Sintering Specific

Additive

tempera- tan δ

Change of resistivity

Composition element

ture ε

20° C.

ε (%)

tivity

No.

x y z wt % (°C.)

20° C.

(× 10.sup.-4)

(-25° C.)

(+85° C.)

(Ω · cm)

__________________________________________________________________________

0.100

0.800

0.100

-- -- 1050 13930

310 +8.4 -54.1 1.2 × 10.sup.13

0.100

0.800

0.100

MnNb

0.20

1040 13010

220 +3.1 -52.3 1.0 × 10.sup.13

3 0.100

0.800

0.100

MnNb

0.80

1020 12150

107 +2.1 -50.1 8.0 × 10.sup.12

4 0.100

0.800

0.100

MnNb

2.00

1000 10840

102 -2.1 -48.1 8.5 × 10.sup.11

0.100

0.800

0.100

MnNb

3.00

1000 9410

215 -2.1 -38.2 2.5 × 10.sup.11

0.100

0.800

0.100

MnW 0.10

1040 13390

280 +7.1 -53.2 1.1 × 10.sup.13

7 0.100

0.800

0.100

MnW 0.50

1030 12840

147 +5.1 -50.4 8.0 × 10.sup.12

8 0.100

0.800

0.100

MnW 1.00

1000 10430

78 +2.1 -46.3 8.0 × 10.sup.12

9 0.100

0.800

0.100

MnW 2.50

960 6440

109 -3.5 -38.4 2.5 × 10.sup.12

10*

0.100

0.800

0.100

MnW 4.00

940 3180

215 -5.3 -30.6 7.5 × 10.sup.11

11*

0.100

0.800

0.100

MnSb

0.20

1040 13380

254 +7.1 -53.1 1.4 × 10.sup.13

12 0.100

0.800

0.100

MnSb

0.50

1040 12860

200 +4.3 -50.4 1.2 × 10.sup.13

13 0.100

0.800

0.100

MnSb

1.00

1030 11430

63 +1.3 -43.7 1.2 × 10.sup.12

14*

0.100

0.800

0.100

MnSb

3.00

1000 7420

212 -3.4 -39.8 5.0 × 10.sup.11

15 0.100

0.800

0.100

MnNb

1.00

MnW 0.50

1000 10840

174 -5.3 -48.3 1.2 × 10.sup.13

16#

0.200

0.700

0.100

-- -- 1000 21350

410 -6.3 -54.0 1.0 × 10.sup.13

17*

0.200

0.700

0.100

MnNb

0.30

1000 20140

280 -5.1 -53.1 1.2 × 10.sup.13

18 0.200

0.700

0.100

MnNb

0.50

1000 18430

172 -3.5 -50.6 1.0 × 10.sup.13

19 0.200

0.700

0.100

MnNb

1.30

1000 16430

74 +0.8 -48.2 8.0 × 10.sup.12

20 0.200

0.700

0.100

MnNb

2.50

1000 11130

168 +4.3 -39.2 6.0 × 10.sup.12

21*

0.200

0.700

0.100

MnNb

5.00

980 6990

254 +5.3 -36.4 1.0 × 10.sup.11

22*

0.200

0.700

0.100

MnW 0.10

1000 20410

313 -3.1 -50.1 1.0 × 10.sup.13

23 0.200

0.700

0.100

MnW 1.00

990 16890

174 -3.1 -50.1 8.0 × 10.sup.12

24 0.200

0.700

0.100

MnW 2.00

980 13380

184 +0.6 -43.2 5.0 × 10.sup.12

25*

0.200

0.700

0.100

MnW 5.00

940 8190

205 +3.2 -39.3 2.0 × 10.sup.11

26*

0.200

0.700

0.100

MnSb

0.10

1000 20030

305 -5.1 -53.1 1.5 × 10.sup.13

27 0.200

0.700

0.100

MnSb

0.50

1000 18630

200 -3.5 -51.2 1.5 × 10.sup.13

28 0.200

0.700

0.100

MnSb

1.00

1000 13340

106 +0.6 -43.9 1.0 × 10.sup.13

29 0.200

0.700

0.100

MnSb

2.50

1000 10140

184 +4.3 -39.3 4.0 × 10.sup.12

30*

0.200

0.700

0.100

MnSb

5.00

980 8430

213 +4.9 -39.4 1.0 × 10.sup.11

31#

0.250

0.550

0.200

-- -- 980 12110

90 +4.4 -55.0 8.0 × 10.sup.12

32*

0.250

0.550

0.200

MnNb

0.30

980 11980

85 +3.1 -51.3 9.0 × 10.sup.12

33 0.250

0.550

0.200

MnNb

0.50

980 10830

35 +2.1 -49.3 8.0 × 10.sup.12

34 0.250

0.550

0.200

MnNb

1.00

980 10400

65 +0.3 -45.3 7.0 × 10.sup.12

35 0.250

0.550

0.200

MnNb

2.50

980 9125

168 +5.4 -39.8 5.0 × 10.sup.12

36*

0.250

0.550

0.200

MnNb

5.00

960 6050

256 +6.9 -37.4 1.0 × 10.sup.11

37*

0.250

0.550

0.200

MnW 0.30

980 11480

84 +3.3 -53.9 1.0 × 10.sup.13

38 0.250

0.550

0.200

MnW 1.50

960 10350

45 +1.2 -49.8 7.5 × 10.sup.12

39*

0.250

0.550

0.200

MnW 3.00

960 9420

212 -4.1 -36.3 4.5 × 10.sup.12

40*

0.250

0.550

0.200

MnSb

0.30

980 11490

90 +4.3 -52.0 9.0 × 10.sup.12

41 0.250

0.550

0.200

MnSb

1.00

980 10640

122 +4.1 -50.6 9.0 × 10.sup.12

42 0.250

0.550

0.200

MnSb

2.00

980 7130

178 +2.1 -46.3 7.5 × 10.sup.12

43*

0.250

0.550

0.200

MnSb

5.00

980 4130

105 +4.0 -50.1 5.0 × 10.sup.11

44 0.250

0.550

0.200

MnNb

0.50

MnW 0.50

980 11430

105 +4.0 -50.1 7.0 × 10.sup.12

45 0.250

0.550

0.200

MnNb

0.50

MnSb

1.00

980 11580

132 +1.4 -42.3 5.0 × 10.sup.12

__________________________________________________________________________

Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y

(Ni.sub. 1/2 W.sub.1/2).sub.z O.sub.3

Note 2: Compositions of the Nos. with asterisk (*) are outside the scope

of the present invention with sharp (#) are included in the claim 1.

Note 3: Additive elements MnNb means Pb(Mn.sub.1/3 Nb.sub.2/3)O.sub.3, Mn

means Pb(Mn.sub.1/2 W.sub.1/2)O.sub.3 and MnSb means Pb(Mn.sub.1/3

Sb.sub.2/3)O.sub.3.

The sintering temperature is selected as the temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20° C. under application a D.C. voltage of 1000 V.

From TABLE 4 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing and containing at least one element selected from the group consisting of Pb(Mn 1/3 Nb 2/3 )O 3 , Pb(Mn 1/2 W 1/2 )O 3 and Pb(Mn 1/3 Sb 2/3 )O 3 in an amount in total quantity equivalent 0.50 to 2.50 weight % exhibit low dielectric loss at the room temperature as compared with that of composition with no addition and exhibit still high dielectric constant along with low sintering temperature.

The reasons for the limitations in TABLE 4 are as follows.

›EXAMPLE 3 · 2 of 2

If contents of Pb(Mn 1/3 Nb 2/3 )O 3 , Pb(Mn 1/2 W 1/2 ) and Pb(Mn 1/3 Sb 2/3 )O 3 in total is smaller than 0.50 weight %, the dielectric loss at the room temperature is not improved. When the content in total is larger than 2.5 weight %, the dielectric loss becomes larger and specific resistivity becomes smaller.

As apparent from these Examples 1 to 4, the ternary ceramic compositions of the present invention have low sintering temperature below 1100° C., so that relatively cheap metal or alloy such as silver-30% palladium can be employed as internal electrodes of multilayer ceramic capacitors, and the durability of furnace used for sintering use may be extended and electric power for sintering may be lowered. Moreover, the ceramic compositions according to the present invention exhibit high dielectric constant together with high specific resistivity, low temperature coefficient of the dielectric constant and low dielectric loss. Therefor, the ceramic composition in accordance with the present invention are suitable for use in ceramic capacitors.

It will be evident that the starting materials to be used in the present invention are not limited to those used in the above-mentioned examples. Other oxide or compounds which are easily decomposed at elevated temperature may be used in place of the starting materials of the above examples.

Claims

3 · 3 independent · depth 1

3 granted claims

›1.independentA ceramic compositions comprising a substance represented by the formula PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3…

›2.independentA ceramic composition comprising a substance represented by the formula PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3 …

›3.independentA ceramic composition comprising a substance represented by the formula PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3 …

Classifications

3 codes

IPC · International Patent Classification

Section C — Chemistry; metallurgy

C04B35/499

USPC · US Patent Classification

501/136501/134

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